Apparatus for bending tube blanks



Dec. 22, 1959 A. A. KLEIN APPARATUS FOR BENDING TUBE BLANKS 3 Sheets-Sheet 1 Filed April 21, 1958 Dec. 22, 19 9 A. A. KLEIN 2,918,102

APPARATUS FOR BENDING TUBE BLANKS Filed April 21, 1958 5 Sheets-Sheet 2 Dec. 22, 1959 A. A. KLEIN APPARATUS FOR BENDING TUBE BLANKS 3 Sheets-Sheet 3 Filed April 21, 1958 Fill-T1 APPARATUS FOR BENDIN G TUBE BLANKS Al ois August Klein, Caldwell, N.J., assignor to Horace T. Potts Company, Philadelphia, Pa., a corporation of Pennsylvania Application April 21, 1958, Serial No. 729,798

14 Claims. (Cl. 15348) This invention relates to apparatus for the bending of tube blanks and has for an object the production of tube bends of substantially uniform wall thickness by compression bending.

Heretofore tube bends, such as elbows and other similar pipe couplings or fixtures, have been formed by either hot bending or cold bending processes. Inthe hot bending process, the hollow tubular blanks have been heated and then forced through dies and over a mandrel. The cold bending process has been accomplished by filling the hollow tubular blanks with various substances, such as liquid, granular material, rubber cores, or flexible metal mandrels prior to the bending thereof and then forcing the tube blank with its filler through a shaping die to form the tube blank into a tube bend of desired shape. One of the preferred methods of the prior art has been to employ a rubber filler which is held under compression during the bending operation so as to exert an outward force on the inner wall of the tube blank as it is moved through the die. To maintain the rubber filler under compression, it has been necessary heretofore to provide a retarding cylinder with a metal mandrel of flexible type so as to pass around the curve in the die and adapted to engagethe leading end of the tube blank as it is forced into the die. The metal mandrel was adapted to engage the leading end of the rubber filler and cooperate with the actuating plunger which engages the trailing end of the tube blank rubber filler so as to maintain the latter under compression. It. is an object of the present invention to cold-form open-ended tube blanks with a filler material having the characteristic of a liquid, but to do so in a manner in which the need for a retarding cylinder andassociated flexible mandrel is eliminated. This. results in a substantial saving in the cost of bending the tube blanks and enables the tube blanks to be formed into tube bends under relatively high pressures with substantially less expensive equipment. i

In carrying out the present invention, there is provided a die cavity of a diameter corresponding with the outside diameter of the tube blank and having a shape corresponding with the desired angle of curvature of the final tube bend. The open-ended tube blank has inserted therein a filler material which under pressure exhibits a fluid characteristic. A plug is inserted in the leading end of the tube blank and abuts against the filler. The shaping. die is sealed to form a leak-proof die cavity. The plug is inserted in the entrance to the die cavityand forms a seal with the adjacent surface of the die. The die cavity is filled with hydraulic fluidand a. pressure is applied to the trailing end of the tube'blank and its corresponding end of the filler material to movethe plug into the die cavity for displacement of the fluid therein. The: forward movement of the plug and tube blank with itsfi-llermaterial increases the pressure on the hydraulic fluid within. the die cavity asthe area within the cavity is. reduced. Apressure relief valve meters off the hydraulic -fluid as. itisdisplacedfrom thedie-cavity and ice maintains the pressure applied to the filler material at a magnitude corresponding to the pressure setting of the relief valve.

For a more detailed description of the invention and for further objects and advantages thereof, reference is to be had to the following description taken in conjunction with the accompanying drawings, in which:

Fig. 1 diagrammatically illustrates one form of apparatus for practicing the invention and shows the tube blank in its preliminary position during the bending process;

Fig. 2 is an elevation view of the forming dies in closed position;

Fig. 3 is a fractional view showing the tube blank in an intermediate position during the tube bending processes;

Fig. 4 is a view similar to Fig. 3 showing the position of the tube blank after it has been formed into a tube bend;

Fig. 5 is a plan view showing a die for forming a-U- shaped tube bend in accordance with the present invention; and

Fig. 6 is a sectional view taken along the lines 6-6 in Fig. 5.

Referring to Fig. 1, there is illustrated a hollow tubular blank 10, which is adapted to be formed into a tube bend, inserted within the entrance portion of a die cavity 11 formed by a pair of die members. The lower-die member 12 is shown in Fig. l and a mating or upper die member 13 is adapted to be positioned thereon, as shown in Fig. 2, and held tightly against the lower die member 12 by any suitable means, for example, as by a press 17. Gasket members 22 are disposed on opposite sides of the cavity 11 and between the die members 12 and 13 for sealing purposes. The rear end of the die cavity 11 is adapted to be closed and has been illustrated in Fig. l in the form of a breech block 14 having a cavity portion 15 therein which communicates with the die cavity 11. The breech block 14 may comprise a separate member which is held tightly against the rearend of the die cavity 11 as by suitable compression means illustrated as releasable clamping means 16, or,-as* in the preferred arrangement, the breech member may 'be formed integral with one or more of the die members, as illustrated in connection with Figs. 5 and 6. When the breech member 14 is separate from the die members it will be understood that other types of clamping means than jack 16 maybe employed, the operation thereof being by any suitable arrangement, either hydraulic, pneumatic or mechanical. To insure that a good seal is formed between the die and member 14, a gasket 23 is preferably employed.

As may be seen in Fig. 1, the hollow tube blank 10 is'filled with a cylinder 18 of material which, when subjected to highpressures, exhibits fluid characteristics. It will be understood that the member 18 may be of various suitable materials such, for example, as soft rubber, either natural or synthetic, or it may be made of synthetic plastic materials which have suitable characteristics, such as polystyrene and the polyvinyl chlorides in their plasticized form and which are sold under varioustrade names, such as Koroseal and Vinylite.

At the leading end of the tube -blank 10 there is provided-aplug member' ZO- which is of generally bullet shape and hasa curvature 200 on the leading'end thereof corresponding to the-radius of curvature of outside bend or'shaping surface 12a of the die 12. This maybe most clearly seenin Fig. 3-where the plug member 20 is positioned at the'bend of the die. The rear-portion 20a of the plug member 20. is adapted to be-engaged by the leading end of the filler member 18 and the --plug member 20 is provided with a groove to receive-a sealto be filled with hydraulic fluid such, for example, as

oil. The hydraulic fluid or oil is contained within a reservoir or sump 25 and a pump P, which is adapted to be driven by a motor M, pumps the liquid from the reservoir 25 by way of pipelines 26 and 27 through a check valve 28 and pipeline 29 to the cavity 15. The member 14 is provided with a discharge passage 30 and a valve 31 for venting the cavity 15 during the filling operation and it is also provided with a discharge passage 32 and valve 33 for drainage purposes. Another'discharge passage 35 is provided and communicates with a relief valve 36, the purpose of which will later be described.

When the tube blank with its filler 18 and plug member 20 are positioned in the die 12 as shown in Fig. 1, a plunger 40 is moved into engagement with the trailing end of the tube blank 10 and the filler 18. More particularly, the plunger or ram member 40 is provided with a pressure applying member 41 which has a shoulder 41a engaging the end of the tube blank 10 and a central portion 41b of reduced cross section which nests within the end of the tube blank 10 and engages the trailing end of the cylindrical filler 18. It will be noted that the leading or forward end of the filler 18 engages the central portion 20a of the plug member 20. However, the shoulder 20b on plug member 20 is spaced a short distance beyond the leading end of the tube 10. This arrangement permits the filler 18 to be highly compressed between the plug member 20 and the pressure applying member 41 as now to be described.

The ram or plunger 40 is adapted to be operated by a piston 45 which reciprocates within a cylinder 46. With the apparatus positioned as shown in Fig. 1, the pump P is adapted to pump oil under pressure by way of line 26 and line 47, through a four-way valve 48 and line 49, to the rear end of the cylinder 46. When the pressure is applied to the piston 45, the ram 40 causes the tube blank with its filler 18 and the plug member 20 to advance through the die cavity 11 displacing the liquid therein and building up the pressure on the liquid as the area in the cavity 11 is reduced. The pressure relief valve 36 is set at a perdetermined pressure according to the material from which the tube blank 10 is made and such pressure is at a magnitude lower than the pressure applied to the trailing end of the tube blank 10 and filler material 18. As the forward movement of the tube blank 10 and plug member 20 through the die cavity 11 builds up the pressure on the liquid within the cavity to the predetermined magnitude, the pressure relief valve 36 causes the liquid to be metered through passage 35 and valve 36 where it is returned to the sump 25, by way of passage 37, thus maintaining the pressure within the cavity 11 at the predetermined magnitude and below the magnitude of the pressure applied by the ram 40.

During the foregoing process the tube blank 10 moves from its initial position, as shown in Fig. 1, to an intermediate position, as shown in Fig. 3, and thence to the final position, as shown in Fig. 4, at which time the tube blank 10 has been formed into a tube bend 10a. During the foregoing movement of the tube blank 10, the gasket 21 on the plug member 20 formsv a liquid-tight seal with the shaping surface of the die cavity 11 and prevents any of the liquid from moving beyond the plug member 20 into engagement with the tube blank .10 or the filler 18. The shape of the plug member 20 is such that it includes a surface 200 which corresponds to the outside curvature 12a of the tube bend and thus is able to pass around the corner of the die cavity 11 without interference.

Since the forming pressure on ram 40 exceeds the back pressure applied by the liquid in the cavity to the plug member 20, there is movement of the tube blank 10 into the forming portion of the die.

By suitably lubricating the forming surface and by using a metal dissimilar from that of the tube blank, the friction developed during the forming of the tube blank is decreased. The pressure employed on the ram 40 may vary with different tube materials but in all cases will be of sufiicient magnitude to overcome friction, resistance to deformation and the retarding or back pressure required to support the tube walls to prevent wrinkling or collapsing.

By maintaining the filler material 18 under pressure during the forming operation, the walls of the tube blank 10 are prevented from wrinkling, buckling and otherwise deforming and the bending of the tube is the result of compressive forces to the substantial avoidance of tensional forces which might otherwise produce cracks and other fractures of the tube blank 10 during the forming operation. The bending of the tube is accomplished without any substantial thinning of the walls of the tube as it is transformed from a straight tube section 10 into an elbow 10a or other curved tube bend.

After the completion of the tube forming operation, as above described, and before removal of the tube bend 10a from the die, the tube bend 10a is subjected to an increased pressure for a sizing operation generally of the type disclosed and claimed in copending application Serial 508,566, filed May 16, 1955 by David E. Armstrong and Thomas J. J. Dunn, issued October 6, 1959 as United States Letters Patent 2,907,102. In the present system this is accomplished by changing the pressure setting to a pressure equal to that applied by the ram 40. For example, this may be accomplished by changing the setting of relief valve 36. The pressure to be applied by the ram 40 will be selected on the basis of the material and wall thickness of the tube blanks. By increasing the pressure on the filler 18 and on the tube bend 10a, the shoulders 41a and 20b are brought into engagement with their respective ends of the tube bend and the shaped tube bend is forced tightly against the walls of the die cavity 11. This insures that the formed tube bend will be brought to the same size of the die cavity 11 before the tube bend is removed from the die.

To remove the liquid from the cavity 15 and the die cavity 11 after decompression, the drain valve 33 is opened, thereby permitting the liquid to return to the sump 25. The decompression may be accomplished by setting the relief valve 36 to zero. After the cavities 11 and 15 have been emptied of liquid and the four-way valve 48 has been turned 90 to connect line 47 with line 50 and cause the piston to withdraw the plunger 40 from the die and return it to the position shown in Fig. 1, the plunger of the clamping means 16 is released by the control lever 16a and the die members 12 and 13 are then opened so that the finished tube bend 10a can be removed therefrom. As the filler member 18 is no longer under compression, it is easily removed from the interior of the tube bend.

It is to be understood that'the valves 28, 31, 33 and 48 may be of the solenoid-operated type so that they may be easily operated from a remote position and in predetermined sequence.

Referring to Figs. 5 and 6, there is shown an improved shaping die for forming a tube blank into a U-shaped tube bend. The die comprises a lower die member and a mating upper die member 61, which is adapted to be positioned thereon as shown in Fig. 6. The die members 60 and 61 are adapted to be held tightly together by any suitable means such, for example, as plates 62 and 63 which are adapted to be connected to the spaced jou l ha i at iwhatg antag -J nn! v, V cates, with a relief v alve such ,as i the, valve $6 shown. in

b jaw .emp s .nohthcwn. as mayibeaeen n i g an i. the ow s .1 fimvided it as ao-vv h. extends around the periphery of the die cavity 65 .and is adapted to receive agasket dd to form a liquid-tightlseal. In this embpdiment it wi ll be notedthat the breech member has been-formed as, an integral pontion 60 a of thedie and is integral with the lower die member d0. As, in the mbodiment shown infig. 1,.the breech portion ma indie eludes a cavity 58 which communicates with the w, e

cavity- 65. -Th e.b r,eech".portip n lla of the die is rbv d (lie cavity 65. The c ayity hti is alsojp dediwith an communi- .plunger 40 is moved intoengagementwith the trailing end .of the tube .blank and the filler. Theshape of plugirnember .enables .it.to pass around the. U-shaped bendin the. shaping. portion of .the die members-b0 and, 6 .Wi hQ interferences and the gasket 21 on the plug member 20 forms a seal with the shaping surfaces of the dies 60 and 61.

After the tube blank has been transformed from a straight section to a U-shaped section, it is sized in the manner previously described and .the liquid withdrawn from the cavity 68 by way of the discharge line 71. The dies 60 and 61 are then opened and the tube bend removed. The filler is then removed from the tube bend.

The present invention enables tube blanks to be formed into tube bends rapidly and at relatively low cost. It enables the blanks to be formed while under high compression by use of the rubber-like mandrel and eliminates the need of the relatively expensive retarding plunger and flexible link-type mandrels formerly employed. Such flexible metal or link-type mandrels have been relatively expensive to manufacture and since it will be recalled that each tube of different size required a different flexible metal mandrel, the saving in cost is substantial.

It will be understood the invention is not limited to the specific arrangements shown, and that changes and modifications may be made within the scope of the appended claims.

What is claimed is:

l. A system for bending tube blanks which comprises a die having a shaping portion corresponding to the tube bend to be formed, said die having an entrance portion into which each tube blank may be inserted, cavity means communicating with said shaping portion of said die for receiving a liquid, a filler material which under pressure exhibits fluid characteristics inserted within and sub stantially filling said tube blank, a plug member adapted to engage said filler at the leading end of said tube blank and form a liquid-tight seal with the surface of said shaping portion of said die between said cavity and said tube blank, a pressure-applying member engaging the trailing end of said tube blank and the corresponding end of said filler, means for applying a pressure against the trailing end of said tube blank to force said plug and said tube blank with its filler through said shaping portion of said die displacing the liquid in said die to form said tube blank into a tube bend, and valve means communicating with the liquid in said cavity means to relieve the pressure on the liquid and maintain the pres- .10 with an inlet J 0 which isadapted to be connected with thepumpl, the latter being shown in Fig, 1,.for introucine th h dra i f u d i e cav 6 a henc .by way of theinterconnecting flowpas s ag efigafinto. the

liquid to'and from said shapingPQIt'iO-n Qo saidjdi predetermined magnitude loyver than the pressure pplied to. thejtrailing endfofls'aid tub blank.

2." A system for bending tube blanksaccording' t9 claim 1 wherein said plug member has'aicurv dsl fi eat leading end thereof adapted to correspond to that of said shaping portion of said die so asto traverse thecnrye in said die without loss of said liquid t'ight seal.

3; Asystemfor bendingtube blanks accordingto claim 2 wherein saidplug member hasa rear portion shap to nestwithin the leading end of said tube blank.

4. A system for bending tube blanks according to claim 2 including gasket means carried by said plug'menther to form said liquid-tight seal wit said sur fac efof said shaping portion .of said die.

5. A system for bending tube blanks according to claim 4 wherein said plug member includesag'rooveand saidgasket means comprises an .Q-rfing within said groove.

6. In asystem for bendingtuhe bla k sfcontain'in g'a filler material having the characteristics of a finid nridelr pressure, a die havinga shapingportion corresponding to the tubebend to be formed, said die ha n'g an entrance portiorfiadjacent ne, end ofsaid shaping portion 'into which "each tube blankmgay be insertedppavity means communicating with the o ther'end ofsaid shaping portion of ,said die for' receiving'aliquidQplug means disposed in the leading endof thetube blank to prevent entry ther' einof the liquid, and fiow connections coniinunicating ,With said cavity means for the pa' ssa ge of, he

maintain the filler material iiithe'tube blarik tinder pressure during the bending operation.

7. A system for bending tube blanks which comprises a die having a shaping portion corresponding to the tube bend to be formed, said die having an entrance portion into which each tube blank may be inserted, cavity means communicating with said shaping portion of said die for receiving a liquid, a filler of rubber-like material inserted within and substantially filling said tube blank, a plug member adapted to engage said filler at the leading end of said tube blank and form a liquid-tight seal with the surface of said shaping portion of said die between said cavity and said tube blank, a pressure-applying member engaging the trailing end of said tube blank and the corresponding end of said filler of rubber-like material, means for applying a pressure against the trailing end of said tube blank to force said plug and said tube blank with its filler through said shaping portion of said die displacing the liquid in said die to form said tube blank into a tube bend, said cavity means having an inlet and an outlet, a pump means for introducing liquid under pressure into said cavity means by way of said inlet, and relief valve means communicating with said outlet of said cavity means to relieve the pressure on the liquid in said cavity means and maintain the pressure against the leading end of said tube blank at a predetermined magnitude lower than the pressure applied to the trailing end of said tube blank.

8. A system for bending tube blanks according to claim 7 wherein said relief valve is adjustable to maintain different discharge pressure values depending upon the material of the tube blanks being formed.

9. In a system for bending tube blanks containing a filler material having the characteristics of a fluid under pressure, a die having a shaping portion corresponding to the tube bend to be formed, said die having an entrance portion adjacent one end of said shaping portion into which each tube blank may be inserted, cavity means communicating with the other end of said shaping portion of said die for receiving a liquid, said cavity means comprising a member adapted to be releasahly held against the shaping portion of said die, and flow connections communicating with said cavity means for the passage of liquid to and from said shaping portion of said die to maintain the filler material in the tube blank under pressure during the bending operation.

i of said die with the tube blank.

' 10. In a system according to claim 9 wherein said means for-releasably holding said cavity means against said'shaping portion of said die comprises a plunger, and means for controlling the movement of said plunger.

11. In a system for bending tube blanks containing a filler material having the characteristics of a fluid under pressure, a die having a shaping portion corresponding to the tube bend to be formed, said die having an entrance portion adjacent one end of said shaping portion into which each tube blank may be inserted, cavity means communicating with the other end of said shaping portion of said die, said cavity means being an integral portion of said die and having flow passage means communicating therewith for receiving a liquid to apply a back pressure to the filler material in the tube blanks.

12. In a system according to claim 11 wherein said die comprises a pairof die members and said cavity means is disposed entirely within. one of said die members.

13. In a system .for bending tube blanks according to claim 11 wherein said shaping portion has a U-shaped curvature, and plug means having an end adapted to be inserted within the leading end of a tube blank against the filler material while the tube blank traverses the shaping portion of said die, said plug means havingv at its other end a radius of curvature corresponding to the outer radius of curvature of said U-shaped portion to permit said plug member to traverse said shaping portion filler material having the characteristics of a fluid under pressure, the sub-combination comprising a die having a shaping portion corresponding to the tube bend tobe formed, said die having an entrance portion adjacent one end of said shaping portion into which each tube blank is'adapted to be inserted, said die comprising a pair'of die members with said shaping portion and said entrance portion being disposed in abutting faces of said die members, sealing means extending around the periphery of saidtshaping portion to provide a liquid-tight seal between said pair of die members, cavity means disposed withinone of said die members and adapted to receive a liquid under pressure, and a flow passage interconnecting said shaping portion with said cavity means for passage of liquid therebetween to maintain a back pressure on the filler material in the tube blanks during a bending operation.

References Cited in the file of this patent UNITED STATES PATENTS 1,943,978 Luce Ian. 16, 1934 1,947,611 Moitke Feb. 20, 1934 2,615,411 Clevenger Oct. 28, 1952 2,701,002 Arbogast Feb. 1, 1955 2,715,432 Wurzburger Aug. 16, 1955 2,756,707 Peters July 31, 1956 

